Under The Scooby Doo (Undertale X Scooby Doo Crossover)
by Luna Moon 201
Summary: As Fred and the gangs meet with Fred's grandparents they all would find out a mysterious and horror tale of a hybrid who once had taken so many lives of the humans after the war between two races. But there are more that the gang will meet. These monsters of the Underground will meet the gang and will team up but when Frisk and Scooby both comes up missing they have to work as one.
1. Into the City

_**A.N.**_ _ **Decide to have this crossover story and this story is a sequel to my last story of Determined to Stand. Anyways I hope you will enjoy this story. I know there is one that has a Scooby Doo and Undertale and I enjoy that story. Yet I'm doing this my own way. With that being said I want to point some things out before we get started.**_

 _ **One is that there will be OCs involve in the story. Beware of that especially since this is a crossover.**_

 _ **Two is that Frisk is a female in this story and Chara is a male. Two complete opposite genders from the two.**_

 _ **Three and final thing there will be some contain spoilers for the game of Undertale. If you haven't played the game or watch someone play the game then don't read it!**_

 _ **Thanks and hope you enjoy this crossover story!**_

* * *

Driving into the city the van with three different color of pink flowers and a large yellow print says "Mystery Machine" on it.

Inside this van is two females one with long reddish orange hair wearing a purple shirt and a pink mini skirt and the other has short brown hair wearing black nerdy glasses and orange sweatshirt and brown mini skirt. Then there are two males one with the blonde hair wearing a white shirt and a red tie driving the van and the other male in the back seat has brown hair wearing a green T-shirt and sloppy brown pants. Also in the back seat is a brown dog with black polka dots on the dog wearing a blue collar with a yellow tag on it.

The female with the glasses said without looking up from her magazine she has about the city they are going into.

"Huh? It has lots of fairy tales of this city especially the one that they are super suspicious of more like fear of."

The girl with the purple shirt ask, "what do you mean by that, Velma?"

Velma pulls her glasses up saying, "there is a legend of a half human and half monster that long time ago use to live with the human and monsters."

The man with blonde hair glance at Velma while keeping his attention on the road, "monsters? Isn't there no such things as monsters?"

Velma nods, "there isn't at all Fred, it's just a legend."

The man with the green shirt and his dog began to shiver, "monsters?! Here in the city!"

The dog spoke, "ronsters! Oh no!"

The girl with the purple shirt turns to face them saying, "don't worry Scooby and Shaggy. There is no such thing as monsters, right Velma."

Velma nods, "that right Daphine there is no such thing."

Shaggy and Scooby both gave a huge sigh of relief.

Daphne looks at Fred and asks, "so why are we coming here?"

Fred shrugs "just because I kinda wanted to."

Velma looks at Fred and asks, "isn't this where your grandparents live?"

Fred nods, "that why I wanted to come here."

Daphne smiles, "oh I see that makes sense."

Fred smiles as he said directly to Shaggy and Scooby, "my grandma makes the best pumpkin pies ever."

Shaggy and Scooby both began to stick their tongues out happily to hear about that. Velma rolls her eyes as she glanced up at Fred.

"You had to say that to them."

Fred shrugs, "just saying."

Daphne and Velma look at each other knowing why Fred told Shaggy and Scooby about the pumpkin pie.

Fred stops by a gas station to get some gas. Once everyone got out Fred went to get the gas while Velma and Daphne went into the building to get something to drink.

Shaggy and Scooby were looking around till they spotted a hot dog stand not far from the grocery store which isn't far from the gas station. They both look at each as they both ran to the hot dog stand. Once they both got there they look around to see nobody around but a sign saying it's open.

Shaggy looks at Scooby and said, "I don't know where the owner of this hot dog stand is."

"Me rither."

Soon a deep voice said, "heya, sorry I'm late I had to help my niece for a moment."

Both look at the stand to see a skeleton wearing a blue jacket with a white T-shirt inside and black shorts with two white stripes on the side of the shorts standing behind the stand. He has white pupils inside his eyes sockets.

Shaggy and Scooby's eyes widened with fear as they both ran off fearing the skeleton.

The skeleton shrugs as he sits in his chair and put his feet up on the stand showing his two pink fluffy slippers.

"Guess there are some humans still don't trust us monsters anymore."

As Fred came back from paying the gas and the girls got their drinks they happen to see Scooby and Shaggy running right into the van screaming.

Fred and the girls look in the van to see Shaggy and Scooby hugging each other shaking really badly.

Daphne ask in worry, "guys what happen?"

Shaggy and Scooby looks at the gang to see their worries. Shaggy got up and told them that he and Scooby met a real skeleton at the hot dog stand. Of course when he finishes explaining the gang did not believe him.

Fred spoke, "well we better get going. And guys there isn't any such things as monsters. Besides the guy was probably dress up for some reason."

Velma shrugs "he's really early for Halloween."

The gang got into the van and drove away from the gas station.

Meanwhile…

As the skeleton fell asleep on the hot dog stand with some people looking at him oddly before going on their day. Just then the phone rang making the skeleton wake up as he almost fell out of his chair. He looks at his phone to see his brother's name on it. The skeleton answer the phone.

"Hello, this is fart master speaking."

"Sans, that wasn't funny and I hope you weren't sleeping on your job."

Sans looks at the hot dog stand and said, "maybe."

"Sans! How many times I have to tell you not to do that!"

"Heh, you know me as the lazybones."

"You are such irresponsible."

"So uh… what did you want, Paps?"

Papyrus gave a loud sigh as he spoke once more, "I came to call you because I wanted to make sure that you knew that I might not be home tonight."

Sans looks at his phone with worry, "why?"

"Because Undyne wants me to be trained for being a better fighter them Mettaton and I'm going out to uh… spend the night."

Sans sigh, "you're sure you want to do this?"

"Of course I am Sans. Besides Mettaton isn't all that bad."

Sans nods, "alright I suppose so. Welp, see ya tomorrow then."

"I'll make sure to call you before I go to bed."

"Thanks, I would like that."

"I'll call you later and don't sleep on the job!"

Sans laughs, "no prob Paps, but you know I'm a such a lazybones."

Papyrus gave an irritated sigh before he hung up the phone. Sans laughs as he put his phone back into his pocket.

After ten minutes his phone began to ring Sans looks at his phone to see Frisk's name on it.

"Welp looks like the kid needs my help on her homework again."

He answers the phone and asks, "need help with a problem, kid?"

Frisk sighs as Sans could tell something is wrong, "kid, Frisk, are you alright?"

"Sans" Frisk spoke slowly, "I suppose I'll tell you later. Since you are probably busy with business."

"Nah, I ain't busy right now. You can tell me. I'm always listening here."

Frisk giggles a little, "it's just I been wondering about that innocent with Chara and Mr. G and I can't help it if they might come back."

Sans sighs as his white pupils disappear, "Frisk, listen you know me and Paps won't let nothing bad happen to you."

"I know but it's just…"

"Stop! You don't need to worry about anything anymore. Besides Kameron had promised us that he'll keep you and all of the races safe from Chara and Mr. G so stop worrying about this."

It was quiet for a while till Sans finally broke the silent.

"Look just forget about all that. I mean we are happy now we don't have to worry about that for a long time."

Frisk sighs as she whispers trying to not let Sans hear, "nobody would understand."

Sans heard her, "what are you saying kid?"

Frisk gasps, "you heard that?!"

"Couldn't help to hear it. I began to think there is more that you don't want to tell me. So what is it? No more secrets."

Frisk was silent for a moment before she spoke, "it's just I don't know how to explain it but I think I'm being treat or more like being stalk."

Sans sat up straight, "what do you mean?"

"It's nothing. Something you wouldn't be able to do."

"Frisk, you know I'll do anything to keep you safe. So tell me what's going on and who's stalking you?"

"I really don't know who but I know there is someone in my dreams and possibly in my head. She keeps on treating me to kill me and she wants to hurt all of you. She never really shows herself but I know by the tone of her voice she's a female."

Sans nods as he listens, "so this girl comes into your dreams? Is she like Chara?"

Frisk began to cry "I don't know! I never saw her or know who she is!"

"Wow, wow, kid calm down. I'm not upset at you. I want to help you too. We can figure this out together."

"Just like before?"

"Just like before kiddo, we can do it."

"Thanks, that means a lot to me. Besides, I never told mom about this."

"It's probably best Tori already has enough on her hand. Do you want me to come over to keep you company?"

"No, I know you're pretty busy."

"Nah, I can be there for you if you want."

Frisk sighs, "no, I'll be okay I'm just glad that you call me."

Frisk hung up as Sans looks at his phone for a while. Then he decides it would be best if he should go check on Frisk to make sure she's okay.

With that Sans close his hot dog stand and grab a couple of hot dogs before he teleported to Toriel's house to check on Frisk.


	2. Grillby's

Fred and the gangs made it to the apartments. They all got out and went into the apartment building. Fred got in the elevator and click the number to get to his grandparents as the whole gang got into the elevator as well. The elevator went up to the third floor before letting the gang off of the elevator.

Soon a small ten-year-old girl with blonde hair with her bangs cover her left eye wearing a red T-shirt and blue jeans look up at the gang smiling.

"Rachel come here darling."

"Okay!"

Rachel ran over to an elderly woman with white and gray curly hair with glasses on wearing a pink and white nightgown. Fred smiles as he knew this woman too well.

"Grandma!"

Fred's grandmother looks up and smiles wide as she hugs her grandson, "oh Freddy you've come back!"

Fred nods, "of course, I wanted to come back to see you and Grandpa."

She smiles, "oh… he's been talking about you."

Fred introduces the gang to his grandmother as he smiles wide at them, "it's so nice to meet all of you."

Velma looks at Rachel, "so is she related to you?"

Fred's grandmother looks at Rachel and smiles, "oh her no, no, she's my next door neighbor's daughter. Rachel always comes to stay with us if her parents are really busy at work."

Rachel sighs, "they are always busy no matter what."

Scooby came up to Rachel and began to lick her making her giggle.

Everyone laughs as Fred's grandmother shows the gang to her apartment as she let them all in, Fred's grandfather wearing blue overalls with a gray sweatshirt inside and bladed saw Fred and gave his grandson a huge bear hug.

"It's been a long time since you came here, Fred. You've grown up super fast!"

"Grandpa you are embarrassing me."

Fred's grandfather let Fred go and smiles seeing the gang, "and what do we have here?"

Fred smiles and introduces the gangs to his grandfather. His grandfather smiles wider as he scratches his white whiskers.

"It's so nice to meet all of you."

Daphne nods, "you too, Fred told us about you."

His grandmother smiles as she pets Fred's head, "of course he did, he never forgets about us."

"Grandma" complain Fred as his face began to turn red.

"You're such a cutie that's all."

Shaggy and Scooby looks at each other than to Fred's grandmother.

Shaggy asks, "Fred says that you make delicious pies."

Fred's grandmother nods, "indeed I do but today I'm all out."

Velma sighs, "well I did happen to see a sign says Grillby's Restaurant a mile away from…."

Velma looks to see Shaggy and Scooby had both zoom right out before she could finish. Daphne laughs as she looks at Fred's grandparents who were giving a confused look.

"Once you say food or restaurant they are right there to eat anything they want."

Velma nods, "literally everything."

Both Fred's grandparents laugh as they sat Fred and the girls on the couch to get to know one another.

In the meantime….

Sans sighs as he walks up to Toriel's house. He got up to the door and knock on the door.

"Knock, knock," he said with a wide grin knowing that Toriel would answer.

"Who's there?"

"Skip"

"Skip who?"

"Can I skip my way in please?"

"Oh, Sans you're always too funny. Please do come in I'm busy making a blanket for Miss. Lavine."

"Thanks"

Sans walks in as he saw Toriel sitting in her purple rocking chair knitting a long blue and white blanket. She looks up as she pulls up her reading glasses.

"What brings you here, Sans?"

Sans looks at Toriel and said, "uh… the kid wanted me to come here today. So is she in her room?"

Toriel nods, "yes she is, though I've noticed she hasn't come out yet to want a pie or perhaps do some training with Undyne and Papyrus."

Sans looks down as he tries his best to not let Toriel see his worry for Frisk.

"Uh… thanks um… I might take Frisk to Grillby's. If that's alright with you?"

"Oh not at all. Thank you for telling me."

"No problem Tori."

Sans teleport himself in front of Frisk's room. He sighs as he knocks on her door that has a sign say 'Frisk' in bold yellow print. He waited for a moment before Frisk had finally answer.

"Yes, mom?"

"Uh… sorry but it's me, kiddo."

"Oh… um… come in then."

Sans opens the door to see Frisk sitting on her bed looking out the window not far from the bed.

"Hey, uh… Are you okay? I mean you kinda had me worry there."

"I guess."

"Hey, I did appreciate for you to tell me of what's going on."

"I just... Don't want anyone to worry about anything."

"Hey, it's okay you can tell this bag of bones anything."

"Heh… I guess you're right."

"Hey, you wanna go to Grillby's to get this off you mind for a while."

Frisk looks up at Sans, "I would love that very much."

"Great, I told your mom about it so she knows we're heading out. I know a shortcut."

Sans reach his bony hand for Frisk to grab, once Frisk grabs hold of Sans' bony hand and got herself up the two of them disappear and appear right in front of Grillby's restaurant.

"Welp, let's see if Gribz is busy today."

Frisk nods as the two of them walk into the restaurant. Once inside the place wasn't to pack which is pretty normal on a Saturday. Sans and Frisk as always sat by the bar table and waited for Grillby to come out and take their orders.

Scooby and Shaggy both walk into the restaurant a minute later. They were about to walk in all the way when they both spotted Sans and Grillby talking. They were about to scream when a girl beside them whispers softly.

"Please don't be scared."

They turn to see a twelve-year-old girl with short brown hair wearing a black jacket inside is a pink and blue stripe shirt and blue jeans. Shaggy looks at this girl with an odd look.

"But they would try to hunt us down and…"

"No" snaps the girl, "they aren't like that. Besides, have you met them yet?"

Both Shaggy and Scooby nervously shakes their heads.

"Well, I think it's about time you do. Monsters and humans must work as one."

"That's what you fool hearters think!"

Shaggy and Scooby looks around as they could see darkness all around them. Both clung together as their whole body began to shake in fear.

The girls sigh hearing that voice, "I remember you. Though I don't know who you are?"

"It doesn't matter Frisk! Besides, you've caused this mess and you'll regret it!"

"Where are we and what do you want?"

The voice sounds like a female voice laughs, "Frisk, you are such a naive child just what Chara said you are."

"You know Chara?!"

"Only by a little. I watch how he possessed your own body and took all those lives from those monsters. Wow, I never thought you would stand up to him one day. Yet again, you were still a weakling to have help from your uncles and the six human souls who lost their lives because of the monsters."

Shaggy and Scooby wished they knew where they are and both can escape. Cause they are pretty freak out.

"Who are you?!" cried Frisk.

The girl giggles, "that's for you to find out later. I may perhaps have that little doggie join ya next time."

Frisk narrows her eyes as she could feel the wind brushing against her hair and her clothes. Even Shaggy and Scooby both can feel the same wind. All of sudden everything went complete black for all three of them.

All three didn't know what had just hit them.

* * *

 **A.N. Hope you all this chapter. Been a while since my last update. Anyways as always so many mysteries to be solved once again. I wonder where this mysterious girl took Shaggy, Scooby, and Frisk. Have to wait and see.**


	3. Been Saved and Oh No!

Shaggy and Scooby saw a light not far from where they are. Frisk tilts her head a little. A bit aware of the light. Shaggy and Scooby had no idea of what is going on.

"Get out of here!"

All three were about to turn but felt somebody pull them away from the light and into the park of the human world. Frisk smiles when she finally turn to see three kids looking at her. Shaggy and Scooby both turn and were about to scream when the girl with the long blonde hair wearing a cowgirl hat and suit wrap her arms around both of their mouths.

"You want us to be found?"

Shaggy and Scooby were confused and scared at the same time of this spiritual girl in front of them. Frisk sighs as she looks up at the boy with blonde hair wearing a brown shirt and a yellow vest.

"Thanks for saving us."

The boy nods at Frisk, "you're welcome. Besides I couldn't stand to see you get hurt again and those two getting hurt along with you."

Frisk looks down, "do you all perhaps knows this girl who took us?"

The boy with the glasses has dark brown hair and wears a dark purple with blue stripe T-shirt spoke up, "uh… oh yeah, we know who…"

His mouth was covered by the boy with light blonde hair wearing a green shirt and brown overalls.

"Ssh… we can't let them know remember?"

"Can't tell us what?"

All four looks at Frisk then at Shaggy and Scooby. The boy with the yellow vest sighs as he looks deeply into Frisk's eyes.

"I'm sorry but I can't risk to telling you about the girl who took you and your new friends here. Besides, all of you are safe now. Let this girl be in our hands."

"But…" Frisk tries to protest.

"No!"

Frisk backs up a little in shock of the boy's reaction. The boy looks at Frisk and sighs kneeling down in front of her.

"Sorry but I can't put you in more danger than you had before. Besides Chara was enough for the both of us to stop anyways. So please don't get involve in this okay? I can't see you getting kill and end up like us."

"Raws," said Scooby in terms he try to say 'us' but it came out wrong since his mouth is being covered by the girl.

Nobody but Frisk pay attention to what Scooby had just said.

"He's right Frisk," said the girl covering Shaggy and Scooby mouth, "we can't risk putting you or the others in danger."

Frisk lowers her head as she pretends to understand. The boy in the vest knew it as he grips on Frisk's shoulder.

"Don't get into this, please. You have to at least try to understand that we're doing this for your own good."

Frisk nods and soon all four kids disappear leaving Shaggy and Scooby speechless.

"Sorry you two had to see that," said Frisk after five minutes of silent.

Shaggy looks at Frisk, "were those ghost?"

"You mean souls? They have been gone for a while. They help me out when I am in need of help. Yet I can't keep out of this. I have to know."

"About the girl who took us?" asked Shaggy nervously.

"Yes, you two don't have to help if you don't really…"

"Hey, there you two are!"

Shaggy and Scooby looks to see Daphne, Fred, and Velma walking over to them.

Shaggy ask, "how did you three get here so fast?"

Daphne answer, "we couldn't get a hold of you two so we decide to use our phones to see where you two are."

Fred nods, "speaking of which. Who is that with you?"

Shaggy and Scooby turn seeing Frisk.

"Oh, that's Frisk we met her at the restaurant until a strange mysterious creature took us."

"What creature?"

Scooby and Shaggy both told the gang the whole story of the girl they only heard of and then the souls came to bring them to the park. Of course, the gang wasn't too convinced by the story but they were willing to help Frisk get back home.

Frisk asks, "Before I go home is it okay if I go check out at this old library?"

Velma nods, "sure but why?"

"I need to find the real true history of this city. I think there is more of this place than anyone knows. Besides it may leads some clue to the girl who took us. If she wants to harm me and Scooby then I'm sure she's going to do it."

The gang looks at each other and nods. Shaggy and Scooby were nervous knowing the three nods. Fred looks at Frisk.

"Then you're not alone. We can help you find out who this girl really is and why she wants to hurt you and Scooby."

Daphne nods, "besides Scooby is a part of our family. We won't let that girl hurt you both!"

Shaggy and Scooby gulp knowing what came next.

Fred said with pride, "gang we have a mystery on our hands!"

Frisk giggles, "you said it like it's almost a daily routine for you."

Velma laughs, "he says it all the time when we go off to solve mysteries."

Frisk smiles, "well that make sense."

Shaggy and Scooby got into the van as Frisk follow them in. Then Fred and the girls got into the front seat. Soon the mystery van drove off as the gang with Frisk had a mystery to be solved and see what is it that this strange girl wants from Frisk and Scooby for.

Meantime…

"Don't worry brother, I'm sure we'll find her" said Papyrus as he petted Sans on the back.

Undyne sighs, "what the hell made her run off?"

Toriel looks at Undyne, "I'm sure she hasn't gone too far."

Sans sighs, "I don't remember saying something that causes Frisk to take off."

Alphys came out, "d… did someone took hold of her?"

Sans looks at Alphys, "what do you mean?"

Even Toriel and Papyrus gave Alphys the same question look at Alphys. Alphys gulp as she tries to think of a way to explain what she think what happen.

"W… well… I… uh… don't quite know… but uh… I um… I…"

Undyne sighs, "it's okay Al, you don't need to explain your reasons."

Alphys nods as she pulls her glasses up and brushes off her black polka dotted dress, "t.. Thank you."

"So" started Sans as he looks up at Undyne seeing her red ponytail hair blowing in the wind, "if she was really kidnapped then where would they want to take her?"

Undyne thought a moment, "well obvious somewhere nobody would find them. Perhaps in the woods."

Papyrus nods, "that's what I began to think! If she did either got kidnapped or ran away that's the first thing I know she would go."

Sans sighs, "good idea, let's just check the woods out."

Toriel nods as she follow the others to the van and they drove towards the woods.

In the meantime...

"You did hear that your daughter is missing?"

"Missing?"

Grillby looks up at the male goat who has long blonde hair wearing a pink shirt with flowers on the shirt and blue shorts. His eyes widened in shock to hear Grillby telling him the news.

"How?"

Grillby sighs, "I don't quite know myself Asgore but Sans turn around to see Frisk was gone. He panics and when I try to comfort him he teleported away."

Asgore nods, "I bet he's with the others to help find her. We should find them and join them to search for her."

Grillby nods, "good idea, what about Flowey?"

Asgore turns to see Flowey sleeping in his brown pot. Asgore shook his head.

"It's best if he stays here. Besides, I doubt he would care if Frisk is gone or not."

Grillby nods as the two took off to join the others to find Frisk.

After twenty minutes Flowey finally woke up and sees that Asgore is gone. He shrugs as he looks up at a big painting of the patterns of golden flowers. Just then a female voice was heard not far from where he was at.

"Hello, Flowey."

"Frisk if that's you this isn't…"

"Frisk? I'm not that dumb girl! Besides, I'm much better than her."

"Wait a minute who the hell are you?!"

"Let me show you who I'm really am."

"Okay?"

Flowey looks to see a tall teenage girl walk up to him wearing a bluish green jacket and blue pants. Her hair is brown and long. Yet the girl isn't normal at all. Her eye on the left is green but on her right is a white hollow socket with a gray pupil inside. Her mouth is stitched except the middle of her mouth and her smile looks like a devil smiling. Flowey gasp knowing who she is.

"You… You must be that… that…"

"Hybrid, yes, the only hybrid that has ever survive the war. The only half human and monster that ever live on this earth."

Flowey gulps, "and what do you want with me?"

"I heard you enjoy being evil. Am I right?"

"And how did you know about me?"

"Let's just say Asriel that I'm friends with your brother Chara."

Flowey's eyes widened in shock. He could not believe that this mysterious girl knew him and Chara so well.

"I'll take you with me so you and I can plan to take down that stupid girl."

"Girl?"

"Frisk, you idiot!"

Flowey narrows his eyes, "that's my line!"

The hybrid grabs Flowey stem and smiles wide, "if you don't shut up then I'll tip this pot over and once you are out I'll make sure to destroy your life forever."

Her right eye pupil began to turn black as black flames formed out of her eye socket, "is that clear?"

Flowey nods nervously as the hybrid let his stem go. Soon the hybrid disappears with Flowey in her hands.

* * *

 _ **AN:**_ _ **Finally got this chapter done. Well, now I'm finally revealing my anti-OC out more now. All you don't know is her name. Don't worry that will come up soon in the story. Poor Scooby and Shaggy are super freak out of what they had just experienced. Bet those two would have terrible nightmares when the day is over.**_


	4. THE END

_**Arthur Note:**_

 _ **Sadly this story will not be continued. Those who enjoy it I'm sorry I just lost the idea and completely forgot about it till I came back but I couldn't come up with any more ideas. However, I'll leave the ending up to all of you! I see so many enjoy it and I do appreciate it really but... do too well every day daily life stuff I don't have to much time to return and get any more ideas. Plus I kinda forgot my OC I was going to put into this story. Wow, genius right?**_

 _ **So whoever is the guest that kept asking me if I would continue this is my answer to you and the rest who are probably asking the same thing but didn't ask in the review. Guess since well... I had other Fanfiction stories I did on my other accounts I just completely forgot about my stories on here. Wow right? Anyways I have a fiction story I'll be doing for next year so... I'll be kinda away from Fanfiction for a while. It also means I'll be off of here for a while too. I might come back once in a while to see if anyone wrote any reviews on any of my stories but... yeah sorry. No more chapters to continue.**_

 ** _From Luna Moon 201_**


End file.
